1. Field of the Invention
The present invention relates to a droplet ejection apparatus and a droplet ejection method whereby ink droplets are ejected onto a medium after depositing an ink aggregating treatment liquid onto the medium.
2. Description of the Related Art
Technology is known in which droplets of ink are ejected after depositing an ink aggregating treatment liquid onto a medium. For example, Japanese Patent Application Publication No. 2007-83180 discloses a small printer which applies a treatment liquid to a medium before the ejection of ink droplets, by using a round cylindrical application roller.
In a small printer, generally, a so-called shuttle type of ink droplet ejection head is used, which moves back and forth reciprocally in the direction (main scanning direction) that is perpendicular to the medium conveyance direction, and therefore intermittent conveyance is carried out by repeating conveyance and halting of the medium at the ink droplet ejection position. In a small printer of this kind, generally, in order to make the apparatus compact in size, the medium is also conveyed in an intermittent fashion at the position of the treatment liquid application roller, in accordance with the ejection of ink droplets, and therefore variation in the application of the treatment liquid arises due to variation in the conveyance speed. Furthermore, since the treatment liquid proceeds to permeate into the medium when the conveyance of the medium is halted, then there is a tendency for the amount of treatment liquid applied to increase. If there are variations in the application of the treatment liquid, then variations in aggregation occur when the ink aggregates, and ultimately, density non-uniformities arise in the image.
A countermeasure considered in order to prevent variations in the application of treatment liquid as described above involves providing a buffer which withdraws the medium (for example, a loop-shaped withdrawal path), between the treatment liquid application roller and the droplet ejection head. By this means, even if the medium is halted at the ink droplet ejection position, it is possible to apply treatment liquid by conveying the medium in a continuous fashion, at the treatment liquid application position, but on the other hand problems arise in that in order to provide space for the buffer, the apparatus becomes large in size and costs increase.
Furthermore, even if treatment liquid is deposited onto the medium by droplet ejection, in cases where the resolution of the droplet ejection of the treatment liquid is made lower than the resolution of the droplet ejection of ink or the treatment liquid droplets are ejected in a thinned out fashion with the objective of saving component costs for the ejection of treatment liquid droplets and saving running costs due to reduced consumption of the treatment liquid, variations in the aggregation of the ink arise due to variations in the amount of treatment liquid deposited onto the medium, similarly to cases where treatment liquid is deposited by application as described above, and hence there has been a problem of density non-uniformities in the image.